The use of aircraft engines having unducted pusher propellers inevitably leads to the appearance of a trail in the airflow encountered by the pylon 101, said trail being produced by the pylon 101 ensuring the structural connection between the aeroplane and the propulsive system and being destined to impact the propeller blades 104 and 105. This event is illustrated schematically in FIG. 2, in which a sectional view of the pylon 101 in its conventional or traditional design and a sectional view of the propeller 104 are shown; in this figure, the speed of the airflow is represented by arrows 201, of which the length is representative of the value of the speed at the point in question. Of course, it can be seen that the speeds at the points located in line with the pylon 101 are less significant than the speeds observed at the points where the airflow is not impacted by the presence of said pylon. These differences in speed give rise to a trail 202, formed by all the points for which the speed of the airflow is affected by the presence of the pylon 101 in the airflow.
The existence of this trail has a number of disadvantageous consequences:                it has a negative effect on performance in terms of fuel consumption;        it has a negative impact on noise level since it constitutes an additional source of noise, this source of noise being particularly bothersome at the moment of take-off of the aeroplane or during the phase of approach of the aircraft;        it has a negative impact in terms of mechanics and vibration by creating an additional source of excitation.        
The prior art proposes solutions to try to minimise the impact of the trail created by the pylon on the blades of the propellers. These solutions include that illustrated schematically in FIG. 3, in which a specific pylon profile 301 has been proposed. The special feature of the profile 301 lies in the shape of its trailing edge 302, which has been truncated compared to a conventional profile of the type visible in FIG. 2. The trailing edge 302 thus has an aperture 303 which is used to blow out the pulsed air 304 at said trailing edge 302. The air thus blown out makes it possible to reduce and even make up for the deficit in speed at different points of the trail of air produced by the presence of the pylon 301, this deficit in speed being illustrated in FIG. 2. To this end, the aperture 303 is fed with pressurised air, for example via a nozzle of the aircraft, which air is depressurised until reaching ambient pressure, thus making it possible to obtain a blow-out.
However, this solution presents a drawback linked to the truncated shape of the trailing edge. Such a shape is detrimental because it increases the shape of the above-mentioned trail when the air is not blown out via the aperture. For reasons of fuel consumption, it is not conceivable to maintain the blow-out during all phases of flight. Thus, although the proposed solution is satisfactory during specific phases such as the take-off or approach of the aeroplane, which are phases of relatively short duration during which the blow-out limits the negative impact, in terms of noise and vibration, of the trail produced by the presence of the pylon in front of the engine propellers, it presents a problem in terms of performance during the rest of the flight owing to the truncated shape of the profile of the pylon.